1. Field of the Invention
The present invention relates generally to anti-piracy of data on optical disks, more specifically, to optical disk having prevention function to protect data on an original optical disk, a method of authenticating such optical disk, and a method of fabricating such optical disk discriminated from a duplicated disk.
2. Description of the Related Art
As information storage medium in the multimedia environment, optical disks have been widely used for storage of music, movies, and software due to their high storage capacity. The optical disks have several advantages over other storage media in that mass-production is possible at a low price and that the quality of information thereon is not degraded even though reproduction or duplication thereof is made repeatedly.
The price of optical disks that are writable once and reproducible in ordinary optical disk players is lowering. Low-priced optical disk fabricating apparatuses have been, moreover, released into the market. Hence, optical disks containing commercial high-priced software tend to be duplicated illegally and spread as pirate disks, resulting in enormous economic loss in the software industry.
Strong policies have been made to inhibit or limit the illegal duplication of optical disks, but perfect prevention of the illegal duplication is impossible because the illegally copied disks can be fabricated readily and distributed privately. Accordingly, technologies are strongly demanded to inhibit illegal duplication of optical disks.
Many methods have been proposed to accomplish the duplication prevention. As one of them, Korean Patent Application S/N. 97-32576, proposed by these inventors, discloses a signal recording method for an optical disk with a copy-protection function and a method of preventing illegal duplication of the optical disk using the recording method.
In the method, a non-standard symbol or an unusual pit pattern is recorded on a prescribed area of an optical disk. The non-standard symbol is formed by shifting or delaying some part of a chosen standard symbol or codeword by a predetermined length, so that it can be equally reproduced as either of two distinct standard symbols. Therefore, an optical disk with one or more non-standard symbols is determined to be a legitimate production if they are reproduced into distinct symbols.
However, in order to form the unusual pit pattern in some areas of an optical disk, the delayed pit pattern must be written precisely into an undefined region, that is, a region located between consecutive pits outside of an allowed limit for normal pits. Accordingly, an optical disk production apparatus with a high precision is required to control the delay of a pit which is chosen to make the unusual pit pattern. However, the high-precise production apparatus costs high, resulting in the increase of the production cost.
The undefined region depends on manufacturers of optical disk drivers. Hence, the unusual pit pattern with the delayed pit is regarded as a non-standard symbol in some optical disk drivers, it is always reproduced as a standard symbol in the others. In the latter case, the desired authentication function does not work even though the optical disk is legitimate one.
It is an object of this invention to provide an optical disk with a duplication prevention function in which a value recorded in a prescribed field of reproduction control data is not coincident with that of the corresponding field of table-of-content (TOC) data, an authenticating method of such optical disk, and a fabrication method of such optical disk.
It is another object of this invention to provide an optical disk with a duplication prevention function in which some of reproduction control data are recorded in the reverse order, an authenticating method of such optical disk, and a fabrication method of such optical disk.
The optical disk with duplication prevention function according to the present invention is characterized in that a value in a prescribed field in a control data needed for reproduction and search is not coincident with that of the corresponding field in a TOC data.
The optical disk with duplication prevention function according to the present invention is further characterized in that some of reproduction control data are recorded thereon in the reverse order.
A method of authenticating the above-mentioned optical disk according to the present invention comprises the steps of reading out a table-of-content data from an lead-in area of the optical disk; extracting subcode data from data recorded in a program area of the optical storage medium; checking whether or not data in a prescribed field of the subcode data is coincident with that in the corresponding field of the table-of-content data; and determining whether the optical disk is a legitimate production or illegally-duplicated production on the basis of the checking result.
Another method of authenticating the above-mentioned optical disk according to the present invention comprises the steps of reading out data of a predetermined size from a prescribed area in the optical disk; checking whether or not some of reproduction control data within the read-out data exist in the reversed order; and determining whether the optical disk is a legitimate production or illegally-duplicated production on the basis of the checking result.
An optical disk according to the present invention is fabricated in such a manner that a prescribed field of a Q-channel data which is collected from header information of a predetermined number of frames has a value different from that in the corresponding field of a TOC data. When the optical disk is loaded in an optical disk driver, a TOC data is first read out from a lead-in area of the optical disk. Then, a Q channel data is obtained from data recorded in a program area of the disk. A comparison is made as to whether or not a value in the prescribed field of the Q-channel data is coincident with that in the corresponding field of the TOC data. The optical disk is judged as a legitimate disk if they are not equal to each other.
An optical disk according to of the present invention is fabricated in such a manner that data to be recorded are written to the optical disk in units of a predetermined size of data, and that reproduction control data corresponding to some of data in the units are written in the reverse order. When reproduction of the optical disk is requested, a predetermined amount of data are read out from a prescribed area of the optical disk and is then divided into several groups of a predetermined size of data. Then, it is checked whether some reversed reproduction control data exist in the data groups. If they are detected, the optical disk is judged as a legitimate production.
The present invention makes it possible to inhibit optical disks which are duplicated illegally from an optical disk of original record from being reproduced, thereby contributing the prevention of illegal duplication.